April 2014

April 28, 2014

Time for a quick roundup of today’s new issue of JCB! Bays et al. describe how phosphorylation of the actin-binding protein vinculin helps cells transmit forces across cadherin-based intercellular adhesions. As explained in this week’s In Focus, adherens junction-localized vinculin molecules (but not vinculin molecules at cell-matrix adhesions) are phosphorylated at tyrosine 822 in response to tension, helping cells to stiffen in response to external forces.

Beguin et al. describe a protein called BARP that disrupts the assembly of voltage-gated calcium channels to inhibit calcium-triggered exocytosis in neurons and neuroendocrine cells. More here.

And in this month’s biobytes podcast, we speak with the authors of two additional papers from today’s new issue. Michael Kessels describes how a protein called syndapin I shapes dendritic spines and synapses (Schneider et al.), and György Hajnoczky explains how mitochondrial fusion supports skeletal muscle contraction – and how this goes awry in myopathies associated with genetic mutations and chronic alcohol abuse (Eisner et al.). You can listen to the podcast below or subscribe in iTunes.

April 14, 2014

In today’s new edition of JCB, Adell et al. reveal how the AAA-ATPase Vps4 helps the ESCRT-III complex form intralumenal vesicles in the interior of multivesicular bodies. Vps4 is known to disassemble the ESCRT-III complex once vesicle formation is complete, allowing the complex to be recycled for further rounds of vesicle production. But Adell et al. show that the ATPase also acts at an earlier step, helping to constrict the neck of nascent ILVs, most likely by remodeling the structure of ESCRT-III filaments. Read more in this week’s In Focus.

Jones et al. describe the architecture of the axon initial segment, a specialized structure that maintains neuronal polarity by preventing axonal proteins from mixing with components of the cell body and dendrites. As summarized here, the researchers use platinum replica electron microscopy to reveal that the segments consist of microtubule bundles surrounded by a dense coat of cytoskeletal proteins such as ankyrin G and spectrin βIV, which may form a barrier to restrict the diffusion of axonal membrane proteins.

Aldridge et al. suggest how chloroplast proteins could induce assembly of the pore complex that transports them across the thylakoid membrane. The twin-arginine translocase (Tat) complex transports folded proteins across the thylakoid membranes of chloroplasts and the plasma membrane of bacteria. As described here, Aldridge et al. perform a series of crosslinking experiments that suggest that substrate proteins insert their signal peptides in between two subunits of the Tat complex, triggering a change in conformation that could initiate pore assembly.

And Hammond et al. develop a new probe to detect the phospholipid PtdIns4P in living cells. Previous probes preferentially detected PtdIns4P at the Golgi, but this new biosensor, based on the lipid-binding domain of a bacterial protein called SidM, also detects pools of the phospholipid at the plasma membrane and on late endosomes and lysosomes. More here.

And Burnette et al. describe how migrating cells flatten out the lamella region at their leading edge by mechanically coupling a contractile actomyosin network at their dorsal surface to ventrally-localized cell adhesions. Authors Dylan Burnette and Jennifer Lippincott-Schwartz discuss their findings in this month’s biosights video, which, for the first time, is available in high definition so you can watch Burnette et al.’s beautiful super-resolution microscopy images in all their glory! It will also make it easier to show the video to your colleagues if you’d like to make use of our Journal Club Pack and discuss Burnette et al.’s paper in your next journal club.

That’s all for today, but you can find all the other papers from today’s new issue on our table of contents page here.

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